Double beta decay Ruben Saakyan UCL 25 March 2004

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 2 Outline  Motivation   status  Situation in the UK  Future projects and UK involvement  Sensitivity and time scale

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 3 Neutrino mass. What do we want to know? e U e1 2 U e2 2 U e3 2 Mixing oscillations  only Hierarchy (-osc and 0) CP-violation (-osc, 0+ 3 H) Relative mass scale (-osc) Absolute mass scale (0+ 3 H+cosmology)  Superbeams -factories ~0.01 eV~0.05 eV> 0.1 eV degenerate invertednormal preferred by theorists

Double beta decay Neutrino nature (Dirac vs Majorana) Absolute neutrino mass scale. Possible sensitivity ~0.01 eV ( 3 H – 0.2 eV, KATRIN) IF degenerate hierarchy, we can measure “everything” 2  0  ~2-3 MeV 48 Ca, 76 Ge, 82 Se, 100 Mo, 136 Xe, 116 Cd, 130 Te, 150 Nd Main candidates:

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 5 The Experimental Problem ( Maximize Rate/Minimize Background) Natural Activity:  ( 238 U, 232 Th) ~ years Target:  (0  ) > years  Detector Shielding Cryostat, or other experimental support Front End Electronics Cosmic ray induced activity Low-energy, ultralow-background eperiment. Overlap in experimental techniques with dark matter, solar ’s UK expertise exists

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 6 Where are we now? < 0.35 – 0.9 eV m scale ~ 0.05 eV mass scale from oscillation experi- ments normal inverted degenerate ~0.01eV ~0.05eV >0.1eV (S. King et al. hep-ph/ )

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 7 Heidelberg-Moscow experiment claim (end 2001) = 0.4 eV ???   community immediate response: Claim is at least premature

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 8 Heidelberg claim. Recent developments hep-ph/ Data acquisition and analysis of the 76 Ge double beta experiment in Gran Sasso accepted for publication in NIM A 71.7 kgyr Data reanalyzed with improved binning/summing Peak visible Effect reclaimed with 4.2 = (0.2 – 0.6) eV, 0.4 eV best fit = (0.1 – 0.9) eV (due to NME) Problems (my view) Looks more like 2.5 of effect Unknown peak at 2030 keV? 214 Bi line intensities do not match  214 Bi unknown

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 9 Situation in the UK  At least 4  experts in UK (3 academics, 1 postdoc)  UCL in NEMO – one of two experiments currently taking data  Sussex, Warwick – COBRA, new approach R&D  Meeting at RAL, Sep 2003 – Interest  decay group > 40 people from particle and nuclear communities

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 10 Situation in the UK   steering group: Sacha Davidson, Brian Fulton, Sean Paling, Ruben Saakyan, James Stirling (chair), Kai Zuber  IPPP workshop April. Think about tackling NME problem   strategy for UK suggested by steering group

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 11 Where to go from here to reach meV? A Great Number of Proposals UK steering group suggested roadmap CAMEOCd-1161 t CdWO 4 crystals DCBANd kg Nd layers between tracking chambers SuperNEMOSe-82, Various100 kg of Se-82(or other) foil COBRATe-130,Cd-116CdTe semiconductors CANDLESCa-48Several tons CaF 2 crystals in liquid scint. CUORETe kg TeO 2 bolometers EXOXe-1361 ton Xe TPC (gas or liquid) GEMGe-761 ton Ge diodes in liquid nitrogen GENIUSGe-761 ton Ge diodes in liquid nitrogen GSOGd-1602 t Gd 2 SiO 5 :Ce crystal scint. in liquid scint. MajoranaGe kg Ge diodes MOONMo-100Mo sheets between plastic scint., or liq. scint. XeXe t of Xe in liq. Scint. XMASSXe t of liquid Xe

Future experiments expected to start in 2008/10 (5 yr exposure) Experiment, cost estimate Source and Mass Sensitivity to T 1/2 (y) Sensitivity to (eV) * Majorana $50M 76 Ge, 500kg3× – 0.07 CUORE $30M 130 Te, 750kg(nat) 2× – 0.17 EXO $50M-100M 136 Xe 1 ton 8× – 0.12 SuperNEMO $30M 82 Se (or other) 100 kg 2× – 0.11 * 5 different latest NME calculations

3 m 4 m (25 G) B NEMO-III SuperNEMO COBRA CdTe, CdZnTe Criteria for choosing projects Competitiveness UK role Complementarity

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 14 Suggested Future UK programme Two steps: SuperNEMO and COBRA  SuperNEMO Quick start due to >15 yr of R&D experience; meV by ~2014, likely to be first; if observed, disentangle mechanism of 0 decay UK one of the main proponents; suggested to host in Boulby mine  COBRA Novel approach; potential for large masses; possibility meV by ~ ; possibility to disentangle  mechanism Idea of Kai Zuber (Sussex) Highly complementary!

25/03/2004Ruben Saakyan, UCL PPAP meeting at RHUL 15 Summary   decay is indispensable for solving neutrino mass puzzle  Great interest in particle and nuclear physics community. Highly complimentary to existing UK neutrino programme  An opportunity for UK to lead  research  We may be not far away from the effect…